1. Field of the Invention
The present invention relates in general to detectors for sensing motion and more specifically to such detectors that employ polymeric piezoelectric sensing mediums.
2. Description of the Prior Art
Devices are known in the art that employ piezoelectric crystals that are weight loaded such that they vibrate during movement of the devices as shown in U.S. Pat. No. 3,456,134 issued to Ko; 3,186,237 issued to Forrest, and 3,667,293 to Moore. The Ko and Forrest patents show weights end mounted in cantilever fashion on the piezoelectric crystals and the Moore patent shows a weight center mounted on the piezoelectric crystals. The sensitivity of such detectors is limited by the rigidity of the crystals which cannot bend very much. Such devices develop rather uniformly distributed piezoelectric charge along their opposite surfaces and consequently, where shown, the electrodes on those surfaces cover substantially the entire surfaces thereof.
U.S. Pat. No. 3,832,580 to Yamamuro et al. shows a mechanical energy to electrical energy transducer utilizing polymeric piezoelectric film in FIG. 7. Its operation, however, is dependent upon compression and extension in a direction within the planar surface of the piezoelectric film. Such device suggests no bending of the film, electrostatic charges rather uniformly distributed along the entire surface of the film and electrodes covering substantially the entire surfaces thereof.